[CH2:1]([O:3][C:4]([C:6]1[C:7]2[C:22](=[O:23])[CH:21]([C:24](=O)[CH3:25])[CH2:20][CH2:19][CH2:18][C:8]=2[N:9](C(OC(C)(C)C)=O)[CH:10]=1)=[O:5])[CH3:2].Cl.[NH2:28]O>CCO>[CH2:1]([O:3][C:4]([C:6]1[C:7]2[C:22]3[O:23][N:28]=[C:24]([CH3:25])[C:21]=3[CH2:20][CH2:19][CH2:18][C:8]=2[NH:9][CH:10]=1)=[O:5])[CH3:2]In a sealed tube were 5-acetyl-4-oxo-5,6,7,8-tetrahydro-4H-cyclohepta[b]pyrrole-1,3-dicarboxylic acid 1-tert-butyl ester 3-ethyl ester (1.1 mmol) and hydroxylamine hydrochloride (2.2 mmol) and 10 mL EtOH. The mixture is heated at 100° C. for 16 hours. The solvent is evaporated in vacuo and the residue is taken up in CH2Cl2 and washed two times with NaHCO3 (aq). The organic layer is dried over Na2SO4 and evaporated in vacuo and the residue chromatographed using 10% MeOH in CH2Cl2 as mobile phase to yield 3-methyl-4,5,6,7-tetrahydro-1-oxa-2,7-diaza-cyclopenta[e]azulene-9-carboxylic acid ethyl ester as a white solid (76%). 1H NMR (CDCl3+CD3OD) 1.3 (t, 3H), 1.90-1.98 (m, 2H), 2.10 (s, 3H), 2.35 (t, 2H), 2.75-2.82 (m, 2H), 4.21 (q, 2H), 7.15 (s, 1H).
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